A study of older women found that those who had the highest levels of the vitamin, found in oily fish and eggs, were nearly 60pc less likely to contract age-related macular degeneration (AMD).

Scientists believe it has anti-inflammatory properties that can help prevent the incurable condition by stopping the eyes being damaged.

However, the researchers recommend that older people talk to their doctors first to see if they need to take supplements. Some studies have warned against taking large amounts of the vitamin because in high doses it is thought to weaken bones.

Protect

The paper, published in 'Archives of Ophthalmology', suggests that one way older people can help protect their eyesight is by ensuring they take enough vitamin D.

Researchers studied 1,313 women aged between 50 and 79. They tested the levels of serum 25(OH)D in their blood, which reflects vitamin D intake, and also asked them about their diet and how much time they spent outdoors.

Years later they re-examined the women to see how many were losing their sight. They found that those aged under 75 who had the highest intakes of vitamin D were far less likely to develop early AMD.

The women who took an average of 18mg a day were 59pc less likely to develop the condition than those who took less than 3mg of the vitamin each day.

This highest intake level is less than the 25mg in a standard supplement pill but more than the recommended daily allowance of 10mg for adults and 15mg for pensioners.